Thread rolling die



May 9, 1933. R. THOMSON 1,907,684 I THREAD ROLLI NG DIE Filed July 3,1931 *2 Sheets-Sheet l 155555 1 50006271005022 BY I ATTORNEYS May 9,1933. R. THOMSON .THREAD ROLLING DIE Filed July 3, 1931 2 Sheets-Sheet 2mm m0 m T fl wN 30 operation;

Patented May 9 1933 UNIT STATES RAT'ENT. OFFICE Bonner 'rnomson, ormmeron, NEW JERSEY, LssIoNoB r DARDELET Tillman Loox conronarron, 01 NEWYORK, N.'.Y., A CORPORATION or DELAWARE THREAD ROLLING DIE Applicationfiled m a, 1931. Serial No. 548,544.

Important objects of the present invention are, to provide improvedthread rolling dies designed for more accurate thread forming; toprovide such dies having ribs arranged for successive engagement withthe work in, a manner to obtain an equalized thread forming actionthroughout the rolling operation; to provide such dies designed tofirmly hold the work in a manner to prevent twisting thereof during therolling operation and consequent inaccurate thread forming; to providesuch'dies designed to prevent twisting of the work by an arrangement ofthe ribs to obtain symmetrical distribution of the points where thethread forming action occurs, so that.twisting moments will beprevented; and to provide such dies designed for more equalizeddistributionof the metal displaced by the rolling operation. Otherobjects of the invention will appear hereinafter.

In the drawings: v Fig. 1- is a face View of one of the dies; Fig. 2- aface view of the other die;

.Fig. 3 an enlarged detail section taken on the line 33 of Fig.1 showingseveral of the die ridges in engagement wit-h a work piece;

Fig. 4 a' side view of the two dies upon areduced scale showin them incooperative.

relation at the beginnlng of a thread rolling Fig. 5 is an upper edgeview of the dies in said relation;'and

Figs. 6 to 13 inclusive, enlarged transverse sections taken on thecorrespondingly num-- bered section lines of Fig. 4 and diagrammaticallyshowing the successive engagements of the thread forming ribs with thework.

The bodies of the dies are flat, rigid plates preferably formed of highspeed steel and shaped forniounting in a standard thread rollingmachine. -The die which is to be mounted in a fixed position in themachine is designated 1 and the reciprocating die is designated 2. Eachhas a rectangular Working face upon which there are thread forming ribsor ridges arranged to form a tapering field. In general outline thefield defines a salient directed toward the leading end of the die. Theridges arenpreferably formed upon the die face by a milling operationand then the die is hardened. It is customary to operatively mountthread rolling dies in vertical planes with one longitudinal edgeuppermost. "In the present instance the ridge fields are formedadjacentthe upper longitudinal edges of the dies and the working facesare flat and smooth below the fields. The .excess depth ofthe dies ismerely to adapt them to their mountings in a machine.

.The dies are intended primarily for hot rolling but they may beemployed for cold rolling also.

The fixed die 1 has its thread forming ridges inclined in accordancewith the desired thread helix angle atone side of the work which is tobe threaded.- As shown,the ridges are varied in length in a certainstepped relation forsuccessive engagement with the Work during a rollingoperation. There is a single ridge 3 of maximum length near the .middleof the field. This ridge extends nearest to the leading end of the die.Above the 4, a single ridge 5, apair of ridges 6, a single ridge 7 and apair of ridges 7 These alternating singles and pairs have their leadingends successively spaced rearward in steps ridge 3 there are insuccessiona pair of ridges each equal to approximately one half thecircumference of the bolt shank or other work piece to be threaded.Below the ridge 3 there are in succession single ridges 8, 9, 10- and11. The ridge 8 has its leading edge spaced rearward from that of ridge3 approximately one half the work circumference and the succeeding ribs9, 10 and 11 have their leading ends spaced rearward in steps each equalto approximately the entire circumference of the work. 7 J

The moving die 2 has its thread forming ridges inclined oppositely tothose of die 1 when in working position; As shown, its ridges are alsovaried in length somewhat similarlyto those of die 1. There is a pair ofridges 12 of equal and maximum length near the middle of the field.Above the ridges 12 there are insuccession asingle ridge 13, a pair ofridges 14, a single ridge 15, a pair of ridges 16 and a single ridge 17.These alterridges 19 merging with the upper edge of the die. Below theridges 12 there are in succession, single ridges 20, 21, 22 and 23having their leading ends spaced rearward from the endsof ridges 12 insteps each equal to aprlo proximately anentire circumference of the workpiece.

In the present instance the thread forming ridges of the two dies have across sectional contour designed for forming a wellknown Dardelet typeof thread disclosed in U. S. Patent No. 1,657,244. The ridges arematerially wider than the grooves between them,

the crests of the ridges make an angle of preferably six degrees withthe die faces and their side faces converge outward slightly. Such dieridges will form, upon a bolt or similar work piece, a male threadhaving a-groove materially wider, than itsrib and a sloping root surfaceadapted for self-locking coaction with a similarly sloping surface uponthe crest of an engaged female thread. This selflocking coaction isobtained by relative crosswise displacement of I the engaged threadsupon relative turning of the threaded memberswithout axial advance. Attheir leading ends the thread forming ridges are beveled, as at 25.

For the performance of a thread rolling op-- eration a work piece is fedbetween the overlapped end margins of the, dies. Here a relievedmarginal portion 24 of the die 2 prevents its escape, and the die 2 ismoved in the direction of the arrow of Fig. 4 or 5 to bring the steppedridges into action successively.

In Figs. 6 to 13 inclusive the sequential engagements of the ridges withthe work piece are shown diagrammatically. In these views the ridges areshown as of V-form in order to simplify the illustration, and where theridges are shown as traveling in grooves or groove convolutions formedearlier in the operation said rooves are represented as larger than theri ges to distinguish them from grooves which are being intially formedby ridges. J The opposed ridges 3 and 12 of the two dies are so locatedthat at the beginning of thethread rollingoperation the leading end ofridge 3 will be disposed directly opposite the" space between theleading end of the ridges 12 diametrically across the work piece W, asshown in Figs. 4 and 6. Thereby the -work piece is held by said ridgesat three points symmetrically located with reference to a line Xperpendicular to the die faces. This symmetrical ridge engagement withthe work piece continues throughout the first half turn of the workpiece. beginning of the second half turn of the work 55 piece, as shownin Fig. 7, one of the ridges At the 12 enters the groove 3. formed bytheridge 3, the other ridge 12 and the ridge 13 start to form grooves atopposite sides of groove 3. Simultaneously,.at the opposite side of thework piece the ridge 3 and one of the ridges 4 enter the grooves 12previously formed by the ridges 12, and the other ridge 4 and the ridge8 start to out new grooves.

It will be seen that the initial thread forming points areagainsymmetrical with respect to line X and that there are now four ofthem, axially advanced one half pitch space at opposite sides of thework piece. At the beginning of the third half turn of the work piece,as shown in Fig. 8,

one of the ridges 14, ridge 13, and the ridge 12 enter the previouslyformed grooves 4, V

12 and 8 and the outermost ridges 14'and 20 start to form new grooves.Simultaneously, at the opposite side of the work piece,

the two ribs 4 and the'rib 3 enter the previously formed grooves 3", 13and 12 and the.

ridges 6' and 9 at the opposite side of the work piece start to form newgrooves while the intervening ridges enter previously formed grooves. Atthe beginning of the fifth half turn of the work piece, as shown in Fig.10, the outermost ridges 16 and 21 at one side of the work piece and theoutermost ridges 7 and 9 at opposite sides of the work piece begin toform new grooves while the intervening ridges enter previously formedgrooves. At the beginning of the sixth half turn of the work piece, asshown in Fig. 11, the outermost ridges 17 and'21 atone side of the workpiece and the outermost ridges 7 and 10 at the opposite side thereofstart to form new grooves while the intervening ridges at both sidesenter previously formed grooves. Thus throughout the major portion ofthe rolling operation the thread forming action at 'both sides of thework piece constantly occurs atpoints symmetrically located with respectto line X. These points advance equally in opposite directions from saidline one half pitch space, or one half the lead of the thread,

tion the ridges 10 and 11 of die 1 and the ridges 22 and 23 of die 2come into successive engagement with the work, as doalso the uppermostridges of the dies.-. v The constantly symmetrical thread form'- ingaction of the dies causes theworkpiece to be held in a manner to preventthe ocgagement with the'work and for pro My improved dies have beendesigned for forming threads of the desired accuracy.

What I claim'is 1. A pair of 'cooperative thread rolling dies havingthread-forming ribs oppositely inclined in accordance with the desiredthread helix angle at opposite sides of the work and having theirleading ends varied in spacing from theleading ends of the dies forsuccessive engagement with the work and for progressive initialthread-forming action at diametrically opposite points of the work 5constantly symmetrical in location with reference to a line through thework perpendicular' to the working faces of the dies.

' 2.-A pair of cooperative thread rolling dies having thread-formingribs oppositely inclined in accordance with the desired thread helixangle at opposite sides of the work and varied in length for successiveenessive initial thread-forming action at diametrically opposite pointsof the work constantly symmetrical in location with reference to a linethrough the work perpendicular to the working faces of the dies and forthe ad-, vancement of said points outward in opposite directions onehalf the thread lead at each side of said line andat each side of thework upon each half turn of the work.

3. A pair of' cooperative thread rolling dies having thread-forming ribsoppositely inclined in accordance with the desired thread helix angle atopposite sides of the work, the medial ribs of the dies being longestand the ribs at either side thereof decreasing in length in definitesteps for successive engagement with the work and for progressiveinitial thread-forming action at diametrically opposite points of thework constantly symmetrical in location with reference to a'line.through the work perpendicular to the working faces of the diesand for the advancement of said points outward in opposite directionsone half pitch distance at each side of said line and at each side ofthe work upon each half turn of the work.

4. A pair of cooperative thread rolling dies having thread-forming ribsoppositely inclined in accordance with the desired thread helix angle atopposite sides of the work, the medial ribs of the dies having theirleading ends nearest the leading ends of the dies and the ribs at eitherside thereof having their leading ends spaced farther from the leadingends of the dies in definite steps for successive engagement with thework and for progressive initial thread-forming action at diametricallyopposite points of the work constantly s mmetrical in location withreference to a llne through the work perpendicular to the working facesof the dies and for the advancement of said oints outward in oppositedirections one half pitch distance at each side of said line at eachside of'the work upon each half turn of the work.

5. A pair of coo V rative thread rolling dies having threadorming ribsoppositely inclined in their working positions in accordance with 'thedesired thread helix angle at opposite sides of the work, the medialribs of the dies being longest, the ribs at one side thereof beingsuccessively shorter in outward steps each equal to approximately thework circumference and those at the opposite side of the middle beingalternatey'shorter in outward steps each equal to approximatelyone halfthe work circumference for'successive engagement of the ribs with thework and for progressive initial thread-forming action at diametricallyopposite points thereof constantly symmetrical in location withreference to a line through thework perpendicular to the working facesof the dies and for the advancement of said points one opposite sides ofthe work and varied in length and arranged to form rib fields upon thedies tapering toward the leading ends of the dies, one of the dieshaving a pair of contiguous middle ribs of maximum length, I the otherdie having a single middle rib of maximum length located for engagementwith the work at a point opposite the space between the said pair ofribs at the opposite side of the work at the beginning of the rollingoperation, ribs at one side pf the middle ribs of the dies beingsuccessively shorter in outward steps each equal to approximately thework circumference and ribs at the opposite side of the middle beingalternate: ly shorter in outward steps-each equal to approximately onehalf the work circumfer ence, for successive engagement of the ribs withthe work and for progressive initial thread forming action atdiametrically opposite points thereof constantly symmetrical in locationwith reference to a line through the work perpendicular to the workingfaces of the dies. and for advancement of said points one half pitchdistance at each side of saidline and at opposite sides of the work,upon each half turn thereof.

7. A pair of cooperative thread rolling dies having thread forming ribsdefining a rib field upon each die tapering toward the leading end ofthe die, the middle ribs of the 5 fields havin their leading endsnearest the leading ends of the dies, the ribs at one side of the middlehaving their leading ends successively farther from the leading ends ofthe dies in outward steps and the ribs at the opposite side of themiddle having their leading ends farther from the leading ends of thedies in alternate succession by outward steps.

8. A pair of cooperative thread rolling dies having thread forming ribsdefining a rib field upon each die tapering toward the lead.-

ing end thereof, the middle ribs of the fields having their leading endsnearest the leading ends of the dies, the ribs at one side of the middlehaving their leading ends altero nately farther from the leading ends ofthe dies by outward steps each equal to approximately one half thecircumference of the work, the ribs of one die at the opposite side ofthe middle having their leading ends in v succession farther from theleading end of the die by outward steps each equal to approximately onecircumference of the work and the ribs upon said opposite side of themiddle. of the other die also having their leading ends farther from theleading end of the die in succession by outward steps, the first stepbeing equal to approximately one half the work circumference and thesucceeding steps being equal to approximately one circumference of thework.

9. A pair of cooperative thread rolling dies i 10. A pair of cooperativethread rolling dies having thread forming ribs defining a rib field uponeach die tapering toward the leading end of the die, the middle ribs ofthe fields having their leading ends nearest .the leading ends of thedies and the ribs at the opposite sides of the middle in both fieldshaving their leading ends spaced rearward by successive outward stepsfrom the middle ribs.

In testimony whereof I hereunto aflix my signature.

- ROBERT THOMSON.

having thread forming ribs defining a rib field upon each die taperingtoward the leading end thereof, one die having a pair of middle ribsstarting side by side nearest the leading end of the die, the other diehaving a single middle rib starting nearest its leaddie with the pair ofmiddle ribs having the ribs at the opposite side of the middle onesstarting in succession farther from the leading end by outward stepseach equal to approximately one circumference of the work and the ribsupon said opposite side of the middle of the other die also startingfarther from the leading end in succession by outward steps, the firststep being equal to approximately one half the work circumference andthe succeeding steps being equal to approximately 'one circumference ofthe work, and the single middle rib being disposed for location of itsleading end diametrically opposite the space between theleading ends ofthe pair of middle ribs upon the other die at the beginning of a rollingoperation.

